This is replacing the TaskFlow task to check when a rabbit node begins to
respond to port 5672. We now use rabbits management plugin and REST API
to check when the cluster is active and able to consume jobs. The new task
is added at the end of the create_cluster flow. This is (arbitrarily) going
to the 0th node's RabbitMQ Management port.
Change-Id: I9dffdefd9cdcd6317f5c3114c59b4b30b8218239